<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>外部js代码</title>
</head>
<body>
    <!-- 单击按钮弹出对话框 -->
    <button id="btnclick">单击 试一试</button>

    <!-- 导入外部js文件 -->
    <script src="./js/03.js"></script>
</body>
</html>